Means for controlling electric motors.



PATBNTED JULY 28, 1903.

R. LUNDELL.

MEANS FOR CONTROLLING ELECTRIC MOTORS.

APPLICATION FILED MAR. 12, 1903.

2 SHEETS-SHEBT 1.

N0 MODEL awumtoz aw-Line we a No. 734,724, PATBNTED JULY 28, 1903. R.LUNDELL. MEANS FOR CONTROLLING ELECTRIC MOTORS.

APPLICATION FILED MAB..12, 1903.

N0 MODEL. 2 SHEETS-SHBET 2.

S/z g AVAVAVW 5 1 flhiAlAA H'VVVV Wm 4% W @23322 THE wams PETERS c0.Pmrouma. wnsmnsmn. o, c.

UNITED STATES Patented July Q8, 1903.

ROBERT IQUNDE'LL, OF NEW YORK, N. Y.

MEANS FOR CONTROLLING ELECTRIC MO'l'OlQS SPECIFIGATIQN forming part ofLetters Patent No. 734,724, dated July 28, 1903.

Application filed March 12, 1903. Serial No. 147.434. (N'o model.)

in a prior United States Patent, No. 716,445,

granted December 23, 1902.

The invention is particularly applicable to electric elevators or lifts,and has for its objects, first, to devise improved means of controlwhich will give to the motor or motors a wide range of predetermined orfixed speeds which are practically independent of the armature-currents;second, to devise improved means for starting the motor or motors andfor automatically accelerating the same up to the lowest fixed speed;third, to devise means for changing the armature-circuits of two or moremotors from series to parallel, or vice versa, Without interrupting thecurrent from the power-circuit and without departing from thepredetermined or fixedspeeds while the circuits are being changed;fourth, to so increase the efficiency of the improved means of controlthat the motors may be employed in connection with elevator-cars whichare overbalanced to a considerable extent and that they under suchconditions may work equally well as dynamos returning current energy tothe power-circuit whenever they are being driven as such by the load inthe car or by the counterweight.

It should be pointed out that if an elevator-car is overbalanced to suchan extent that the counterweight is equal to the weight of the car plusone-half of its maximum load the motor or motors need only besufficiently powerful to either propel or retard fifty per cent. of thefull rated load of the car. For this reason it becomes \erydesirable tooverbalance the car and to provide motive power of such a character thatit will either consume or deliver electric energy, according to thenature of the load. External resistances in field-winding F.

the armaturecircuit must in this case be dispensed with, as the motorwould accelerate too rapidly when driven as a dynamo with any externalresistance in its armature-circuit. Any speed corresponding to a runningposition of the controller must be made fairly.

independent of the nature of the load-that is, the speed must be nearlythe same when the motor works as a dynamo as when it works as a motor.

,It will be understood from the above remarks that a motor which has tofulfil the dual function of dynamo and motor must have a wide range ofpredetermined or practically fixed speeds, with the minimum speed so lowthat the external starting resistance or other starting appliances mayautomatically be cut out as soon as the inertia of the moving apparatusis overcome.

Referring now to the drawings, Figure 1 is a diagram of the circuitconnections between a power-circuit, a pair ofdirect-currentcompound-wound electric motors with various resistances inconnection therewith, and the stationary contacts of a controller havinga main and a reversing cylinder in addition to some auxiliaryelectromagnetic switches. This figure illustrates also the developedmovable contacts of both the main and the reversing cylinder. Fig. 2shows in detail the various circuit connections between the armature andthe field windings of the motors and their regulating resistances at thedifferentpositions or notches on the controller.

Referring now to the drawings in detail, and particularly to Fig. 1, Aand AA represent two similar armature circuits or windings on the samecore, and F Sh represent the respective series and shunt windings forthe field-magnet in which the above-mentioned armature-core is supposedto be running. A and AA represent two other similar armature circuits orwindings upon another core supposed to be running in anotherfield-magnet, for which F and Sh represent the respective series andshunt windings.

Sr represents a starting resistance for both motors.

r represents a low resistance, which (when in circuit)practicallyshort-circuits the series r is a similiar short-circuitingresistance for the field-winding F b, c, and (1 represent highresistances for regulating the current through the shunt field-windingSh, and b 0 and 61 represent similar resistances for the shunt-windingsSh of the other motor.

L+ and L represent the positive and the negative mains from apower-circuit.

O represents an electromagnetic startingswitclnwhich also serves as acircuit-breaker, D another electromagnetic switch for shortcircuitingthe starting resistance, and M and M represent additionalelectromagnetic switches for closing by-paths around the rerespectiveseries windings F and F of the two. motors.

B represents the brake-coil otan electromagnetic friction-brake for themotors,which is only released when a current flows through said coil.

R represents a small and sensitive relay which is adapted to break thecircuit through the brake-coil B and the coil of the startingswitch 0whenever the electromotive force between the current-mains becomeshigher than the proper electromotive force for which the relay has beenadjusted.

1 2 13 14 to 28,inclusive, represent the stationary contacts for thereversing switch or cylinder.

f 'm 972 &c., to act inclusive, represent the stationary contacts forthe main circuit-changing and speed-controlling cylinder.

3 and 4 represent other stationary contacts for the samecylinder,adapted to close a shuntcircuit through the brake-coil B andthe coil of the starting-switch O.

5 6, &c., to 12, inclusive, represent other stationary contacts for themain cylinder, adapted to control the currents through theshunt-windings Sh and Sh of the two motors.

On the left-hand side of Fig. 1 is shown a development of the movablecontacts of the main cylinder. Lines in dot and dash are drawn acrossthe various contact positions or notches, and the running positions arespecially pointed out by the numbers 1 2 3, (50., to 11, inclusive.

Fig. 2 shows in detail the various circuit connections which correspondto the abovementioned running positions. It will be noticed that thesame letters as in Fig. 1 are employed to indicate similar parts.

It will be supposed that if the apparatus is used in connection with anelectric elevator the reversing and the main cylinders are eitherrotated electrically by means of socalled pilot-motors or manually bymeans of some suitable rope connection between the car and thecontroller, or by any other means known in the elevator business.Assuming now that the reversing-switch has been closed in any one of itstwo positions for up or down and that the main switch is at its 0Eposition that is, at line 0 O of Fig. 1 attention is first called to thefact that both shunt-fields are now weakly energized. The

current flows through the shunt-fields as follows: From Llto stationarycontacts 3 and 9, where it divides itself, one circuit leading throughresistances d, c, and I) through the shunt-field Sh to the stationarycontacts 1, 2, andf to L, the other circuit leading from the stationarycontacts 9 to 8 through resistances d 0 and 5 through the othershuntfield Sh and in a similar manner to L. Attention is also called tothe fact that the lower contacts of the reversing-switch have closed theground or the negative connection for the electromagnetic switches C andD. The main cylinder may now be rotated from its off position O O. Thefirst movement of the same establishes connection between thecontacts 3and 4, thereby causing a current to flow from Llto 3 and 4 through E andC to contacts 1 and 2 to L, This current will release the friction-brakeat the same time as it will close the electromagnetic starting-switch O.The first movement of the main cylinder has also caused the resistancesd, c, and h, as well as d 0 and b ,t0 become short-circuited, which inturn causes the shunt-fields Sh and and Sh to become strongly energized.A circuit through the motors is now established as follows: FromLlthrough starting resistance Sr to the stationary contacts tand a-|through armature-windingAto cont-acts aandact+ through armature-windingAA to contacts aa, .9, and 03-}- through armature-winding A to contactsa and acF-lthrough armature-winding AA then by the wire w through theseries field-winding F to contacts f u, and f+, through the other seriesfield-winding F to f, and, finally, to L, precisely as shown in detailin Fig. 2. position.)

Attention is now called to the manner in which the electromagneticswitches O and D are interconnected. It will be Seen from inspection ofthe drawings that the sWitchD is dependent upon 0 and that it cannotclose until the switch 0 has been closed. However, as soon as C isclosed a current will flow through the coil of D, closing its contactsand causing the starting resistance S1" to become short-circuited. Thisstage of the circuit connect-ions is clearly illustrated by the nextcircuit diagram in Fig. 2. As the starting resistance is short-circuitedthe electromagnetic switches M and M will receive full potential acrosstheir coil-terminals and will now close quickly. The said switches arearranged to short-circuit the series field-windings F and F through thelow resistances r and 7", thereby causing the field strength and thespeed of the motors to become practically independent of thearmature-currents. The circuit connections are now as shown at theposition marked first speed in Fig. 2.

It will be understood from the above that the motors will be acceleratedautomatically up to the first predetermined or fixed speed by theinterconnected or interdependent switches O, D, M and M as soon as these(See the starting switches are once started by a slight movement of themain cylinder. It should be pointed out that if the motors are to bedriven as dynamos the starting resistance Sr will of course cause asmaller drop in the applied electromotive force than when the motors areto work as motors. The electromotive force across the coil-terminals ofthe switches M and M will consequently rise faster when the motors workas dynamos, which in turn will cause these switches to close sooner--infact, the switches M and M will under the abovementioned conditionsclose almost as soon as the switch D. The second speed is obtained by afurther movement of the main cylinder. The circuit connections are fullyillustrated by the diagram in Fig. 2. It will be noticed that the fieldstrength of one motor (motor No.1) remains the same as for the firstspeed, whereas the field strength of the other motor (motor No. 2) hasbeen very much reduced by means of the resistances b and d which havebeen introduced into the shunt field-circuit. This operation has ofcourse reduced the counter electromotive force of motor No. 2, resultingin an increase in the speed of the two motors,which are mechanicallyconnected by means of the gearing. The third speed position reduces thecounter electromotive force of motor No. 2 to nearly zero, as its shuntfield-circuit is opened and the remaining field strength is now only dueto the short-circuited series field-winding F The fourth speed positioncloses a by-path around the second motor, as shown in Fig. 2, and thespeed of the two motors is now about double the speed at the firstposition. The main cylinder is so arranged that the instant before theabovementioned by-path is closed the short circuit around the seriesfield F is opened at m (See Fig. 1.) This causes the second motor tobecome a plain series-wound motor, which can be short-circuited, as iswell known, without the least trouble. The fifth speedposition isarranged to open the armature and the series field of the second motorand to again close its shunt-field through the resistances b 0 and d Itis also arranged to weaken the shunt-field Sh of the first motor, sothat the speed at the fifth position will be higher than at the fourth.At the sixth speed position the above-mentioned second motor isconnected in parallel with the first motor, as shown by Fig. 2. Theseries field F is not yet short-circuited and serves to automaticallyadjust the field strength of the second motor at the time thearmature-circuit is reconnected to the power-circuit. The speed,however, is fixed by the first motor, the series field of which is stillshort-circuited. The shunt-fields Sh and Sh are now alike in strength,the resistances 1) plus a and 6 plus 0 being alike. The speed has ofcourse increased from the fifthposition, because the shunt-field Sh ofthe first motor (the controlling one) has been weakened. At the seventhposition the second motor becomes the controlling one as to speed. (SeeFig. 2.) It will be noticed that the series field F has again beenshunted or short-circuited, thereby causing the speed to becomepractically independent of its armature-current. The shunt-field S72 isfurther weakened by the additional resistance d causing an increase inthe speed. The armature-circuits of the first motor are opened at thisposition, and the shunt-field Sh of the same is strengthened by cuttingout the field resistance 0. The eighth position cuts out the remainingfield resistance 1) and connects the two armature-circuits A and AA ofthe first motor in parallel to power-circuit, with the series field F inseries, for the purpose of caus-v ing the field strength of the saidmotor to become self regulating, so that the speed of the same may suitthe speed of the second motor, which is still the controlling one as tospeed. At the seventh or the eighth position the speed is approximatelyfour times as great as at the first position. At the ninth position thesecond motor is again out out and the first motoris made the controllingone, as Fig. 2 clearly indicates. The speed has been increased from theeighth position, because the field strength of the controlling motor hasbeen weakened. At the tenth position the armature-circuits of the secondmotor are connected in parallel to the power-circuit with the seriesfield F in series for the purpose of cansing a sclf-adjustmentof fieldstrength, as previously described. Both shunt-fields are of coursealike, as shown by the figure, and the speed has again been increased byreason of a further weakening of the field strength of thecontrolling-motor. The eleventh or the top speed is obtained by runningthe motors in parallel with Weak shunt-fields. The series fields F and Fare short-circuited by the low resistances r and rZwhich cause the topspeed to become fairlyindependent of the armaturecurrents. The saidresistances r and 1' are so proportioned that a small amount of currentis allowed to flow through the series windings for the purpose ofcausing the motors to divide the load properly. The speed at theeleventh position is about eight times higher than at the firstposition. I

It should be understood from the foregoing description that the speed ofthe motors at any one position of the controller is predetermined orpractically independent of the armature-currents and that the motors maybe worked as dynamos without any great difierence in speed. The dynamospeed will of course be somewhat 'higher than the motor speed at a givenposition of the controller, but not enough to cause a sudden jump ineither acceleration or retardation. When the electromotive forceappliedto any armature-circuit is changed or about to become changed,the arrangement is such as to cause the other motor to be controlling asregards speed, and when the armature-circuit of any one motor isreconnected to the power-circuit after being disconnected the fieldstrength of the said motor is caused to become self-regulating at themoment the circuits are reestablished. This prevents asudden rush ofcurrent and consequent shock to the apparatus. A sudden rush of currentis also prevented by the inductive resistance of the seriesfieldwinding,which is fully utilized at the time of the aforesaidchanges.

The relay R (shown at the lower right-hand side of Fig. 1) serves tointerrupt the circuit through the brake-coii B and through thestarting-switch or circuit-breaker 0 whenever the electromotive forcebetween L and L becomes greater than the maximum electromotive force forwhich the relay has been adjusted. The operation is substantially asfollows: The motors may be supposed to be working as dynamos, beingdriven as such by the load. If the current from the power-circuit shouldfail owing to a fuse being blown or otherwise, it will be understoodthat the electromotive force of the motors (being driven as dynamos)would rapidly increase, because of the fact that they cannot now feedback any current energy into the power-circuit. In other words,themotors would cease to become effective as regenerative brakes and wouldrapidly increasein speed. However, as soon as the electromotive forcebetween L and L (see Fig. 1) becomes too great the little relay R willovercome the tension of its adj usting-springyand willcausethecurrentthrough the brake-coil B and the coil of the circuitbreaker Gto be interrupted at x. This will in turn cause the circuit-breaker O tosever the main circuit and will cause the frictionbrake to be applied,bringing the apparatus to rest.

I have shown and described two motors having double-wound armatures forthe purpose of obtaining an extra wide range of speed, and it will beunderstood that the electromotive force applied to each individualarmature winding or circuit is either equal to onequarter or one-half orequal to the full voltage of the power-circuit. Similar results can ofcourse be obtained without departing from the main principles of myinvention by using four motors with single-wound armatures or by usi'ngtwo motors with single-wound armatures in combination with the twodifferent voltages in a three-wire system of distribution. My claims aretherefore not to be limited by reference to a double-wound armature.

Having thus described my invention, what I claim, and desire to secureby Letters Patent of the United States, is-

1. The combination with a power-circuit and two compound-wound electricmotors, of acontroller provided with means for changing theelectromotive force applied to the individnal armature-circuits andadditional means while the electromotive force applied to the armatureof the other motor is being changed.

2. The combination with a power-circuit and two compound-wound electricmotors, of means for changing the armature-circuits from series toparallel and additional means for keeping the current from thepower-circuit closed through one of the motors while the armaturecircuitof the other motor is disconnected preparative to a change from seriesto parallel.

3. The combination of a power-circuit and two electric motors havingshunt field-windings in circuits independent of one another andarmatures arranged to be connected in series or in parallel, with meansfor keeping the power-circuit closed through one of the motors while thearmature of. the second motor is disconnected, and additional means forregulating the field strength of the second motor independently of thefield strength of the first-mentioned motor at the time the armaturesare changed from series to parallel.

4. The combination of a power-circuit, two electric motors having theirfield-magnets energized independently of each other and independently ofthe armature-currents, with a speed-changing controller having thefollowing elements: (a) means for changing the electromotive forceapplied to the individual circuits; (b) means for keeping thepowercircuit closed through one of the motors while the electromotiveforce applied to the armature of the second motor is being changed; (0)means for regulating the field strength of the second motorindependently of the field strength of the first mentioned motor at thetime the electromotive force applied to the armature of the second motoris being changed. 7

5. The combination with two electric motors having their shuntfield-windings connected independently of one another to a source ofcurrent-supply and a controller for changing the armature-circuits ofthe said motors from series to parallel, of means for reducing theexcitation of the shunt-field of one of the motors to a minimum andadditional means for closing aby-path around the armature of the saidmotor before the above-mentioned armature-circuits are changed fromseries to parallel.

6. The combination of two or more com pound-wound electric motors thespeed of which is chiefiy governed by changes of the electromotive forceapplied to the individual armature-windings and a controller havingmeans for weakening the shunt-field of one of the motors and additionalmeans for closing a by-path around the armature and the seriesfield-windings of the said motor before a change in the electromotiveforce applied to the armature of the said motor is effected.

7. The combination of two or more electric ICC motors havingfield-circuits independent of one another, a power-circuit, aspeed-changing controller adapted to change the electromotive forceapplied to the individual armature-circuits, means for keeping thecurrent from the power-circuit closed through one motor while theelectromotive force is being changed for the other and additional meansfor keeping the field strength of the motor which remains in circuitpracticallyind ependent of the armature-current for the purposedescribed.

8. Two or more electric motors arranged to be connected in series or inparallel or to receive varying voltage across their armaturecircuits, incombination with means for keeping the current from a power-circuitclosed through one motor while the armature of another motor isdisconnected, and additional means for causing the field strength of thefirst-mentioned motor to remain practically independent of itsarmature--current while the field strength of the other motor, thearmature of which is disconnected, is made self-regulating orself-adjusting at the time 7 its armature-circuit is reestablished.

9. Two or more electric motors the speed of which is chiefly varied bychanges in the electromotive force applied to the individualarmature-circuits and by variations in their field strengths, incombination with means for keeping the current from a power circuitclosed through one motor while the armaturecircuit of another motor isopened, and additional means for causing the field strength of thefirst-mentioned motor to remain practically independent of itsarmature-current while the armature-circuit of the other motor isopened.

10. Two or more electric motors having their field-magnets energizedindependently of their armature-currents; in combination with means forconnecting the armature-circuits in series or in parallel and additionalmeans for automatically cutting out the starting resistance and forautomatically accelerating the speed of the motors to a predetermined orfixed rate of speed.

11. Two or more electric motors the speed of which is chiefly varied bychanges in the electromotive force applied to the individ-' ualarmature-circuits; in combination with means for varying the fieldstrengths of the motors independently of their armature-currents andadditional means for automatically cutting out the starting resistanceand for automatically accelerating the speed of the motors to apredetermined or fixed rate of speed.

. 12. Two or more electric motors the speed of which is chiefiy variedby changes in the electromotive force applied to the individualarmature-circuits; in combination with means for varying the fieldstrengths of the motors independently of their armature-currents andadditional means for automatically applying a brake when theelectromotive force of the motors exceeds the electromotive force of thepower-circuit owing to a break in the said circuit.

13. The combination of one or more motors capable of returning currentto a powercircuit when driven as a generator or generators, with a relayarranged to actuate an electromagnetic brake when the electromotiveforce of the motor or motors exceeds the amount for which the relay hasbeen adjusted.

14. The combination of one or more motors capable of returning currentto a powercircuit when driven as a generator or generators, with a relayarranged to actuate an electromagnetic brake when the power-circuit isaccidentally interrupted.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ROBERT LUNDELL.

Witnesses:

O. J. KINTNER, M. F. KEATING.

